Meter.



PATENTE) AUG; 25, 1908.

w, LLLLDYD.A

METER.

APPLIUATION FILED 00122, 1905.

l Invero-Zoff" )4W/iam JQ-Lloyd,

UNITED STATES PATENT OFFICE.

WILLIAM J. LLOYD, 0F RUGBY, ENGLAND, AssiCN'oR To GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

METER.

Specication of Letten Patent.

Patented Aug. 25,` 1908.

Application led October 2, 1905. Serial No. 280,914.

v'through the armature of the meter motor which-is immersed in mercury and mounted for rotation in thefield of a permanent or electro-magnet so that .the armature .tends to rotate at a s eed proportional to .the current flowing in t e circuit. The'. rotation of the armature is retarded by eddy currents generated4 in the armature by its rotation in the' magnetic field, or by a separate disk on the meter shaft rotating in an additional ield. As thus 'constructed the meter would give a very accurate registration of the current iowingv in the circuit were it not for the dis-v turbing iniuence of Huid friction, which increasing as the speed of rotation of the armature increases makes the readings more and more inaccurate as-thecurrent to be measured increases.

The obj ect of my invention is to overcome this objectionable characteristic by `providing means for .compensating forthe Huid friction.

In accordance with my invention I provide the meter motor with means for developing an additional driving torque which is proportional, Vor approximately so, to the square of the current to be measured, the

amount of this torque being so regulated as to be suiiicient to compensate as nearly as practicable for the retardation of the motor armature due to the friction of the mercury in which it is immersed.. This additional torque is obtained by means of a coil connected in series with the armature of the motor and arranged to. develop a magnetic field independent of the permanent magnet which reacts upon the current in the armature so as to give a rotational effect suflicient to compensate for the retarding effect' of the The compensating magnet is preferably not only independent of thel permarient magnet, but placedon the opposite side ofthe armature to reduce to a minimum the liability'of the perman'ent'magnet being afiicted by the'current in the compensating co1 The novel features of my inventionwill be denitely indicated. in the claims appended hereto.

The details of the construction and the mode of operation of my improvedfmercury meter will be better understood by reference to the following description taken in connection with the accom anying drawings which illudt'ate one .embo iment of4 my invention and in which` A Figure 1 is a front view of the meter'with arts in section on line 1-1 of Fig-2; and 2 is a section of themeter on line 2-2 of Referring to the'drawings, the parts ofthe meter are inclosed in a casing consisting of a back'l and cover 2 the latter being provided with a window throughwhi'chthe dial 3 may be seen. Secured tothe back l' is a member 4 of iron or other material of good magnetic permeability the lower ortion of whichextends forward horizontally and is of circular shape. This horizontal portion forms the bottom plate 5 of the mercuryreceptacle. Directly above the bottom plate 5 is a disk 6 of insulating material space dapart from plate 5 by a washer 7 also of insulating "material so as to form between the disk 5 of iron and the disk' of insulating material a shallow circular chamber in whichthe armature 8 of the meter motor is adapted to rotate in a bath ofv mercury. Armature 8 is carried by a shaft 9 mounted for rotation -in suitable bearin s 11 11 and Carryin. a weight 12 which o sets the buoyancy o the armature when immersed in the mercury. Shaft 9 also carries a Worm 13 whichrrie'shes with a wormwheel 14 and; thus drives the dial train 3 of the meter. In the 'disk 6 is an opening and one end of a pole-piece 15 iits tightly into this opening and extends in proximity to the armature 8; the other end of the pole-piece is -secured in any suitable manner to one end of a permanent magnet'17. The-other end of magnet 17 is secured to the plate 5 which formsfthebottom of the mercury chamber so that a strong magnetic field is developed passing through the armature 8 and the mercury bath between the pole-piece 15 and theA -meter is connected in circuit in the usual manner. A lead extends from the binding-post 1,9 through the Washer 7 to the niercury chamber and at a. point diarnetrically opposite lead 21 also entends through the Washer 7 to the mercury chamber se that the current flows from binding-post 19 through lead 2Ol to the mercury then diametrically across the armature 8 and out by ther lead 21. Above 'the'disl 6 l lprovide' the coil' rf2/to compensate for the fluid friction, This coil is connected in series with the armature S between the binding-posts 18 and 19 by having one lend connected to the lead 21nand the 4other. connected bya lead L3 with the bind ing-post 18'. 4 The coil,22 is so Wound vand 'andin proximity to the armature 57S. The

' cated on the side of sli-aft 9 opposite from `that of pole-piece 15, as shown in .lfig` '1, and

positioned that it produces a magneticl flux across the disk armature vwhich interacts With the current in the armature to produce a v torque assisting that due to the field of the permanent magnet 17 and the current. inthe armature. If desired, lcoil may 'be mounted on a soft iron core 2-1, the lower end of Which may be embedded in the disk 6 or may extend-through an opening in the 'disk -upper end of core 24 may be connected tothe 4member 4, as'shown in Fig. se as to reduce the reluctance of the pu th for the flux of coil 92. Coil 22 and core 24am preferably lothe current to be measured is arranged to coil on the-opposite side.

l scribedwill beweadily understood. current tobe measured increases the speed of iiow d iametrcally across the armature S so that the torque due to the permanent magnet v17 is eirerted on one side of the shaft andthe torque of the fluid friction compensating 1n this Way coil 22 is removed as far as possible from the permarient-magnet so as'to decrease the danger of changes in the strength of the permanent magnet`17- resulting from the passage cessive currents through the .cuit-22'.

The .operation pf,ithe"n'i/eter as thus def'is the rotation-of armature 8 increasesv and with it the retarding effect of fluid friction. How

" ever, as thecurrent to be measured increases the torque-producing effect of coil 22 also increases since this coil is connected inseries With thearmature 8 and the coiliis so proportioned-that the reaction of the fluit' due tothe '.coil on the` current in armature S develops a torque which just compensates for the disturbin influence ofv the'fluid friction. Since the co' 22 and the armature' S are connectedl in series,the torque developed thereby varies l `approximately with the square of the currentl flowing throughgthem. The b raking effect 'of eddy currents generated in the disk armature' by its rotation in the iield estab' ceases lished by coil 22 also increases approximately with the square 'of the yarmature speed which is proportionalto the current flowing therethrough. But owing f' to i. the low speed of the moving element of the meter and the low density of the flux of coil v22 this retarding effect is very sin-all and is unimportant.

lt will be apparent that the invent-ion may be'carrie'd out in different Ways fromthat above described and that it is not limited in its operation to the particular form of meter Which 1 have chosen for purposes of illustration; l therefore do not Wish to be understoodas limited to the construction which 1 have shown. 2'l

What l claim as new', land desire to secure by Letters Patent of the United States, isf- 1. An electric meter comprising means for establishing a magnetic field,` a receptacle containing a conducting liquid located iii said held, an armature rotatable in said re ceptacle, leads entering said receptacle and haring their ends electrically connected by the conducting liquid and the armature, and

a coil coiiiiected'in series With the armature and arranged to produce an independent magnetic field tliroi'igh the armature and iiitluencing the armature at a portion thereof uniiiiluenced by the other magnetic field.

2. i An electricmeter coiiiprisinga perinal nent magnet., a receptacle containing a conducting liquid located in a ield produced by said magnet, an armature rotatable in the receptacle, leads entering the receptacle and arranged to be electrically connected independent of the permanent magnet through ,the conducting liquid and the armature, and

an electromagnet having its energizing coil connectedy in series. With the armature and ico arranged to develop magnetic flux intersect-' y ing the armature at a portion thereof unin-l i `'l'luericed by the permanent magnet.

v3. An electric meter comprising a recap- `.my hand this'22nd day of September, 1905'.

VILLIAM J. LLOYD.

Witnesses:

ERNEST HARKER, .e S. Gr. WEBB.- 

